Jay,
to add to Sarah, I would just say to feel free to alternate often between barbell and dumbbell bench presses. for inclines, don't exceed a 45 degree angle on the bench, or you shift too much focus onto the delts. I wouldn't worry too much about doing decline bench press, but flat or incline bench dumbbell flyes would be a nice finishing move. Or dumbbell pullovers (start light). cable crossovers are really nice if you've already done a lot of work, and just want a little more pump.
also keep in mind that if you have too high a bodyfat %, it will hide the muscle definition.
If you feel you are already slender/skinny/low bodyfat, then increasing the size of the muscles through exercise is the trick.
Not everyone has the genetics for a super defined 'washboard' stomach. some people only have a 4-pack, others an 8-pack...and it's not always symmetrical.
Abs are definitely the trickiest area, because you need strong abs, and a single digit bodyfat % to really make them stand out at their full potential.
good luck!